When you run a theme it changes the look of the windows for all your programs as well. It may have messed up a setting in Maya that controls the GUI. My render problem was due to a bad setting in the preferences I had loaded, so apparently a lot has to do with the preferences and settings in Maya that determines how it works.
Try this. DONT CHANGE THEMES! :p
Dave Baer
Professor of Digital Arts
Digital Media Arts College
Boca Raton, Florida
dbaer@dmac.edu